USGS - science for a changing world

New York Water Science Center

bullethome bulletinformation/data bulletprojects bulletpublications bulletdrought bulletflood bulletnawqa bulletcontact

Percent Exceedance is the probability that an event/measurement/calculation will exceed a specified reference level recorded over a period of time or over the period of record.

    For Groundwater:

    • For example, percent exceedance is the percentage of April groundwater levels at a site over the period of record (ever measured in April at that site) that are equal to or greater than the current April water level measurement for that site. An exceedance of 40 percent for April means that 40 percent of the April measurements ever made at this site are higher than the current (WY 2008) April water level measurement at this site (or conversely 60 percent are lower).

    For Surface Water:

    • For example, percent exceedance is the percentage of December monthly mean discharges for the period of record at a site (all December monthly means ever measured at the site) that are equal to or greater than the current December monthly mean discharge for that site. An exceedance of 40 percent for December means that 40 percent of the December monthly mean discharge values ever calculated for this site are greater than the current (WY 2008) December monthly mean discharge (or conversely 60 percent are lower).

USGS Home Water Resources Biology Geography Geology Geospatial

Accessibility FOIA Privacy Policies and Notices

USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: http://ny.water.usgs.gov/infodata/percentexceedance.html
Page Contact Information: GS-W-NY_Comp@usgs.gov
Page Last Modified: Wednesday, 03-Mar-2010 12:21:42 EST